Tunnel kiln



G. F. WILDE TUNNEL KILN May 9, 1950 Filed Dec. 10, 1946 GEORGE F- W/LDE Patented May 9, 1950 UNITED STATES PATEN T OFFICE George F. 'Wilde, Ewing Township, Mercer County, N. 3.

Application December 10, 1946, Serial No. 715,274

7 Claims. '1

My invention relates to tunnel kilns for use in the ceramic industry, and particularly to methods "and means for moving articles to be fired through such kilns.

It has been usual heretofore to provide tunnel kilns with tracks along which cars are moved to carry the articles to be fired through the kiln. Such cars are generally heavy in construction, and are provided with relatively thick slabs of ceramic material for supporting the ware so as to prevent distortion or sagging of the support under the high temperature to which the cars and ware are subjected. However, even with such constructions, the cars often jerk or tilt as they are moved through the kilns and the supports for the ware sometimes break or sag su-fiiciently to cause the ware to topple overand produce a jam within the kiln. Moreover, if the cars are pushed through the kiln one after "another any obstruction to movement of the cars tends to cause the cars to buckle up-or to hedorailed. It is then necessary to allow the whole kiln to-cool down before the fallenor broken ware or the displaced cars can be removed safely and the kiln prepared forrenewed operation.

The use of such heavy constructions also 'is objectionable because the car and the support usually weigh much more than the ware itself, and therefore a greater amount of the heat is .required to raise the car and support to the firing temperature than is used productively in 'firing the ware. This not only renders the process expensive, but also makes it .necessary to employ a relatively long kiln-or to move the ware through the him very slowly in order to allow time for the car and support as well as the ware to be brought up to the firing temperature and to permit them to cool down suiliciently alter firing to prevent crazing of the ware when it is removed from the kiln. Such slow operation is particularly objectionable when the kiln is used for deccrating ceramic ware since the pigments orcolors used for decorating purposes are sometimes volatile and therefore are evaporated or partially destroyed before they are fused and fired onto the ware. tend to become dul-lor flat inappearance and to lose much of their attractiveness.

In accordance with my invention, these objections to constructions of the prior art are overcome, and means are provided for moving ware through a tunnel kiln whereby the loss of heat in raising the temperature of the car and support is reduced materially, and the temperature of the ware may be raised and re'ducedcom .paratively quickly so as to permit the use or a Under these conditions the decorations shorter 'kiln and avoid deterioration of the colors used indecorating ceramic ware. Moreover, the economies effected in the use of heat in the kiln render it economically feasible to employ electric heating elements which are capable of the most accurate control and are economical to use in the construction of the kiln.

These results are preferably attained by providing a novel type of car and-support which may be made of light-weight and highly conducting materials such as stainless steel or other high melting point metals or alloys, or light weight and strong ceramic :materials, and by employing means ior supporting and connecting the cars to each other in -a manner which prevents buckling or jamming of the car or jerky or irregular movement thereof as the ham is passed through the kiln.

One of the objects of my invention is to provide a novel "type of means for supporting and moving ceramic ware through a tunnel .kiln.

Another object of my invention is to reduce the amount of heat and the length of time vrequired ior firingor decorating ceramic articles.

A particular object of my invention is to pro 'vide a tunnel kiln with means for supporting and moving articles therethrough in a manner to substantially eliminate interruptions in the operation of'the kiln.

These and other objects and features of my'invention will appear :in the following description thereof in which reference is made to the figures of the accompanying drawing.

In the drawing:

Fig. 1 is Ia perspective of a typical form of tunnelkiln embodying my invention;

Fig. 2 an enlarged longitudinal'sectional view through a portion of the tunnel kiln illustrated in Fig. l;

Fig. 3 is a vertical sectional view taken line 3--3of 2.;

Fig. 14 is a perspective of an alternative form of guide member embodying my invention, and

Fig. 5 is a perspective of a further alternative form of guide member embodying my invention.

.In that form of my invention chosen for purposes of illustration, the tunnel kiln is indicated generally at 2, and is provided with heating means such as the electrical resistors indicated diagrammatically at 4. The ware to be fired is passed into the kiln through the inlet end 6 and is discharged from the :kiln at the outlet end -8. Doors iii are provided for closing the inlet and outlet ends of the kiln :but are movable to the raised positions shown to allow the ware to pass on the into-and out-of the kiln.

The means provided for moving the ware through the kiln in accordance with my invention includes the tracks l2 and M which are preferably in the form of stainless steel channel members and are located in parallel relation on the floor of the kiln and extend longitudinally through and beyond the opposite ends of the kiln. The tracks present continuous parallel upwardly facing channels along which guide members [6 such as cylindrical or tubular rods are movable. Any desired number of tracks may be used to provide an adequate support for the ware but as shown two tracks are generally sufficient for use in a kiln employed for decorating ceramic ware.

The guide members shown in Figs. 2, 3 and 4 are made in short lengths, say from 18 inches to 3 feet in length, and preferably are formed of a metal such as stainless steel or other alloy capable of withstanding extremely high temperatures without undergoing distortion or rapid deterioration on long exposure to high temperatures. The guide members are employed in pairs or groups, one being positioned in each track, and the ends of the tubes are aligned so that they may be engaged by the pusher member iii of the pusher mechanism 20.

Any suitable form of pusher mechanism may be employed, but as shown in Figs. 1, 2 and 3 the pusher mechanism is located adjacent the inlet 6 of the kiln and the member i8 extends transversely of the tracks I2 and i4 above the same in position to engage the outer ends of the guide members [6 located in the channels of the tracks. The pusher member I8 is mounted upon a bracket 22 carried by a bar 24 which is provided on its lower face with a rack 26 engageable with the pinion 28. The bar 24 is mounted on the slide bearings 30 and is advanced by the pinion 28 from the dotted line position of Fig. 2 to the full line position shown in successive cycles of operation. The pinion 28 is mounted on the shaft 32 and is connected by means of a clutch 34 to a shaft 36 driven by the pulley 38 from a motor 40 and reduction gear 42. The clutch 34 is provided with a handle 44 which is movable to connect and disconnect the pinion carrying shaft 32 to the motor driven shaft 36. When the clutch is disconnected, the bar 24 and pusher member I8 may be moved freely away from the ends of the guide members and to the right as seen in Fig. 2. The

projecting ends of the tracks l2 and M are thus cleared to receive another pair or group of guide members in abutting relation with the ends of the preceding guide members. Successive pairs of guide members are thus arranged on the tracks and pushed through the kiln one after another and are removed from the tracks at the outlet end of the kiln and returned to the inlet end for another passage through the kiln.

The guide members described serve as cars or carriages for moving the supporting means 45 on which is carried the Ware 48 to be fired or decorated. The supporting means shown are in the form of plates formed of stainless steel or other thin, light material capable of supporting the ware without undergoing distortion at the high temperatures to which the ware and support are subjected. The sheets 46 may be secured rigidly to the guide members I6 as by welding or otherwise as indicated at 5B in Fig. 2. However, the supporting means preferably are separable from the guide members as shown in Fig. 4 so that the supporting sheets may be placed on and removed from the guide members after the guide members have been placed in the channels of the tracks I2 and I4. Furthermore, by forming the supporting means separate from the guide members, the guide members and sheets are capable of limited relative movement as they travel along the tracks. The guide members therefore can move so as to follow an lateral irregularities in the tracks or they may shift in position relative to the supporting means to pass over rough spots or other irregularities in the track without jerking or otherwise disturbing the supporting means and Ware.

When pushing such light weight guide members and supporting means through the kiln the tracks I2 and i4 hold the guide members in position against lateral displacemnt from their aligned positions. However, there is always a possibility that such separable elements may buckle upward if there is any material resistance to longitudinal movement thereof, such as that due to an obstruction or rough place in the track along which the guide members are moved. When the ware itself is not very heavy such upward buckling of the guide members and supports may take place quite readily. In accordance with my invention this danger is overcome by providing the guide members with interengaging elements which serve to hold the guide members in longitudinal alignment. In the construction illustrated in Figs. 2, 3 and 4 the guide members are in the form of tubes and connecting rods 52 are inserted into the tubular guide members and into positions in which they project beyond the ends of the guide members and from one tube into an-- other. The rods thus extend beyond the abutting ends 54 of adjacent tubes as seen in Fig. 2 and positively prevent relative vertical movement of the tubes and of the supporting mean carried thereby. By similarly connecting all of the longitudinally aligned guide members throughout the length of the kiln the members are in efiect interconnected so as to form a single assembly which prevents buckling of the relatively movable elements.

As shown in Fig. 5 the guide members may be in the form of solid rods or bars 56 each of which is provided on one end with a reduced portion 58 and provided on the opposite end with a complementary recess 60 designed to receive the reduced portion of a succeeding guide member.

In using the construction described for firing or decorating ceramic ware, the kiln is raised to the desired temperature by the heating elements 4. The pusher member I8 is then drawn back to its dotted line position as seen in Fig. 2 and the tubular guide members l6 are placed in the upwardly facing channels of the tracks [2 and 4. The clutch handle 44 of the clutch 34 is then operated to connect the pinion carrying shaft 32 to the motor driven shaft 36. The pinion 28 then rotates to move the rack 26 and bar 24 along the slide bearings 30 to carry the pusher member [8 to the right as seen in Fig. 2 and to push the guide means along the tracks and into the end 6 of the kiln.

When the supporting means 46 are fixedly secured to the guide members, the placing of the guide members on the tracks serves to position the supporting means horizontally to receive the ware 48. In the alternative, if the supporting means is separable from the guide members, the supporting means are placed on the guide members and the ware is arranged so as to be carried therewith into the kiln.

In either case the guide members, supporting :means and ware are advanced by the pusher member 3| 8*until it-hefpaiits are-substantia 1 the position :shown in 11117111155 inFi The clut h :34 :is :then operated to disconnect {shaft 32 :from shaft '36 and the bar 211 and lpllShel member are drawn back to themlotted lineposition. iconnecting rods 5.2 are then inserted approximately half way into :the ends :of the preceding tubular guide members so that the remaining half of the connecting rods project lfrom the rear ends of the guide members. Another pair :of guide memhers is then slipped rover the projecting ends ,of the connecting :rods and "positioned :in the channels of the tracks 12 and M. The supporting means and additional were are then placed in position :to be advanced :by the new pair of guide members and the clutch 3-4 .is operated to cause the assembly to be pushed into the .kiln. Inthis way successive :guiide members and supporting means are passed one after another through the kiln and a substantially continuoussupply of ware is advanced from the inlet 6 through centrally heated zone of the kiln to the outlet end 9 thereof.

When the fired warezreaches the discharge end be returned to the inlet end of the kiln and reassembled to receive additional ware to be fired.

With this construction and operation, the weight of the guide members, connecting members and supporting means is relatively insignificant 'as compared to :the weight of the ware being fired. The heat employed in firing the kiln therefore is utilized almost exclusively .in raising the temperature of the ware and in firing the glaze or decorative material. The low heat capacity of the elements employed for moving the ware through the kiln thus assures high thermal efiiciency of the kiln, and as a result it is economically feasible to heat the kiln by the use of electrical resistors or other relatively high cost forms of heating means.

My invention is particularly useful in the decorating of previously fired ware in that it is possible to bring the ware up to the necessary temperature for firing the glaze or fixing the decorative material very rapidly, and but little heat is required for raising the temperature of the article moving means. For this reason the pigments or other decorative material are fired and fused before they undergo appreciable evaporation or decomposition. Bright, attractive colors are therefore obtainable, similarly the ware may be cooled relatively rapidly, and without awaiting prolonged cooling of the kiln or article moving means. As a result the length of the kiln may be materially reduced, and the time of the firing operation is considerably shortened. It will thus be seen that the cost of the kiln, and the cost of the firing operation may be considerably below those heretofore necessary either for firing or decorating ceramic ware Similarly, the type v(of pusher mechanism, .clutch and drive mployed may :obviously be varied i con- :siderablr. and nume ou other dorms :of tracks. guide members, supporting means and connectine elements may be mnlovcd- @I ew he it should be understood that :the embodiment of my ,mvention :herein shown and describedv is intended to be (illustrative only and is not intended to limit the scope of my invention.

I claim:

:1. .-A tunn l n h ving a pair of parallel tracks extending from an inlet end {of the kiln to an outlet end thereof in the ware receiving gportion of the1 i ,..& plurality f elon ated uide members each formed to extend longitudinally :of said "tracks :and sseparable one from another :so that pairs of said guide members may be placed :on

from the inlet end to the outlet r6116. thereof. :a

were supporting member :carried by each of said pairs .(if guide {members and spanning said tracks,

and means releasably interconnecting :said guide members to hold said members in alignment during their movement through the kiln but -36!- :ara'ble to hermit removal of said guide members from other guide members adjacent thereto when the supporting means and ware emerge from the outlet, end of the kiln.

2. A tunnel kilnhavin la pair of parallel tracks extending longitudinally therethrough from an inlet end to an outlet end :of the kiln and each presenting an upwardly racing :channel in the ware receiving portion of the a plurality of pairs of elongated but relatively short :g-uide members arranged in longitudinal alignment in said channels ,withthe ends of reach pair of guide members in alignment transversely of said tracks, a supporting means spanning said tracks and carried by each of said pairs of guide members for receiving ware to be fired, means for pushing said pairs of guide members along said tracks and through said kiln, and separable connecting means extending from one guide member of a pair to a longitudinally adjacent guide member for holding said guide members in alignment during their movement through the kiln said connecting means being separable to permit removal of said guide members from other guide members adjacent thereto when the supporting means and ware emerge from the outlet end of the kiln.

3. A tunnel kiln having a pair of parallel tracks extending longitudinally therethrough from an inlet end to an outlet end of the kiln and each presenting an upwardly facing channel in the ware receiving portion of the kiln, a plurality of pairs of elongated but relatively short guide members arranged in longitudinal alignment in said channels with the ends of each pair of guide members in alignment transversely of said tracks, a supporting means spanning said tracks and carried by each of said pairs of guide members for receiving ware to be fired, means for pushing said pairs of guide members along aid tracks and through said kiln, said guide members each having complementary projecting and recessed means extending parallel to said tracks and arranged in separable interconnected relation for holding said guide members in longitudinal alignment said connecting means being separable to permit removal of said guide members from other guide members adjacent thereto when the supporting means and ware emerge from the outlet end of the kiln.

4. A tunnel kiln having a pair of parallel tracks extending longitudinally therethrough and each presenting an upwardly facing channel, a, plurality of pairs of relatively short tubular guide members arranged in longitudinal alignment in said channels with the ends of each pair of guide members in alignment transversely of said tracks, a supporting means carried by each of said pairs of guide members for receiving ware to be fired, means for pushing said pairs of guide members along said tracks and through said kiln, and rods positioned within said tubular guide members and extending from one tube to another to hold said guide members in alignment.

5. A tunnel kiln having a pair of parallel tracks extending longitudinally therethrough and each presenting an upwardly facing channel, a plurality of pairs of relatively short tubular guide members formed of metal which is resistant to temperatures to which they are subjected within the kiln, said guide members being arranged in longitudinal alignment in said channels with the ends of each pair of guide members in alignment transversely of said tracks, a sheet of metal resistant to temperatures to which it is subjected within the kiln carried by each of said pairs of guide members for receiving ware to be fired, means for pushing said pairs of guide members along said tracks and through said kiln, and rods positioned within said tubular guide members and extending from one tube to another to hold said guide members in alignment.

6. A tunnel kiln having a, pair of parallel tracks extending longitudinally therethrough and each presenting an upwardly facing channel, a plurality of pairs of relatively short tubular guide members formed of metal which is resistant to temperatures to which they are subjected within the kiln, said guide members being arranged in longitudinal alignment in said channels with the ends of each pair of guide members in alignment transversely of said tracks, a sheet of metal resistant to temperatures to which it is subjected within the kiln carried by each of said pairs of guide members for receiving ware to be fired, said sheet being separable from the guide members to permit limited relative movement of the sheet and guide members during their travel through the kiln, means for pushing said pairs of guide members along said tracks and through said kiln, and rods positioned within said tubular guide members and extending from one tube to another to hold said guide members in alignment.

'7. Means for supporting ware as it is moved through a tunnel kiln comprising carriages, each of which embodies a pair of tubular metal guide members arranged in parallel positions and formed to engage tracks in the kiln, a sheet of metal supported by said guide members for receiving the ware to be fired, said sheet being loosely engageable with said guide members to permit limited movement of the guide members relative to the sheet, and longitudinally extending metal connecting members located in the tubular guide members and carried thereby for holding the guide members in longitudinal alignment with other carriages when passed through a kiln.

GEORGE F. WILDE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,532,017 Wry Mar. 31, 1925 1,562,441 Curtis Nov. 24, 1925 1,713,851 McDougal May 21, 1929 1,802,235 Campbell Apr. 21, 1931 1,923,729 Hull Aug. 22, 1933 

